Added manage_gunicorn flag.

This will allow a user to stop the module from trying to do anything
with gunicorn.
added manage_gunicorn docs
Merge pull request #49 from jalli/master

Add compatability/support for pip 1.5 and fix erroneous rebuilds
Version 1.5.0
Merging master
Revert to using /tmp fir for cwd for virte inst.

If the virtualenv target directory does not exist before running the virtualenv
command the puppet command will fail if the cwd does not exist, hence revert
back to using the /tmp directory for current working directory.